Portable electronic devices, such as notebook computers, typically generate relatively large amounts of heat during normal operation. To prevent malfunctioning of these devices due to thermal overload, it is typically necessary to control the temperature at critical locations in the devices. In desktop computers, the problem of thermal control is more easily solved through the use of fans, cooling slots in the chassis, and relatively large heat sinks.
In battery-powered portable computers, it is undesirable to use fans because of their power consumption, acoustic and electrical noise, and physical size, and because of space limitations, it is undesirable to use cooling slots and large heat sinks. Typical portable computers therefore achieve thermal control through the careful layout of components, and by controlling power consumption. One of the primary ways in which power consumption is controlled is by reducing the frequency of clock signals within the central processing unit (CPU) of the portable computer. A 50% reduction in the frequency of the clock signals will typically reduce the CPU power consumption and heat generation by approximately 50%.